Geology Reference
In-Depth Information
organic matter transformation and the GHI (Gross Heat Impulse
4
) value.
The following zones were distinguished by Waples (1989):
1. Oil generation (grade
MC
1
-MC
3
); GHI value of 15 to 160.
2. Condensate and wet gas generation zone (grade
MC
4
-AC
2
);
GHI value of 160 to 65,000.
3. Late-catagenetic methane generation zone (grade
AC
3
-AC
4
);
GHI value of 65,000 to 972,000.
4. Carbon dioxide, nitrogen and other gases (of metamorphic
origin) generation zone (stage
MG
- metagenesis); GHI
value of over 972,000 (Waples, 1980).
Table 6.4 is based on the temperature vs. depth correlation, which allows
for an objective comparison. This Table shows good agreement between
the results obtained by using the Kartsev
et al
. and Waples scales. There
are small discrepancies in the depth of initial generation zone (grade
MC
1
).
In addition, Waples scale indicates an absence of oil-generation zone in
the Pliocene-Quaternary sequence. These discrepancies may be a result
of impossibility to account precisely for the rate of deposition in the ini-
tial model. In general, however, the Waples's model appears to be more
accurate.
The evaluation of region's oil and condensate geochemical age, con-
ducted utilizing the Reznikov's (1967) technique, supports these general
conclusions. The ages, as calculated by us (Rachinsky, 1973) for the oils
in the fields of the basin's west flank, are 94 to 175 MMY and for the con-
densates are 80 to 115 MMY. A comparison of these ages indicates: (1)
an epigenetic origin of these oils and condensates within the enclosing
Pliocene-Quaternary and Paleogene-Miocene series (Umbaki, Arzani-
Klych, Adzhiveli, Nardaran-Suleiman fields) with the respective reser-
voir ages of 8 and 56 MMY; (2) their qualitative (age) identity; and (3) the
physicochemical match of the thermobaric conditions mostly typical of
the present-day depth of underlying Mesozoic complex. Figures 6.1-a and
6.1-b illustrate the above calculations and indicate that oil and condensate
gradually become younger on moving from the basin's flank toward the
central zone (greatest subsidence).
Assigning mostly Mesozoic age to the hydrocarbons of Productive Series
(PS), Chockrakian Horizon and Maikopian Fm. does not contradict the
aforementioned partial participation of the Paleogene-Miocene complex
4
After Lopatin.
